9/19/06 hofstra university – overview of computer science, csc005 1 combinational circuits gates...

9/19/06Hofstra University – Overview of

Computer Science, CSC005 1

Combinational Circuits

Gates are combined into circuits by using the output of one gate as the input for another



Combinational Circuits

Because there are three inputs to this circuit, eight rows are required to describe all possible input combinations

This same circuit using Boolean algebra is (AB + AC)



Now let’s go the other way; let’s take a Boolean expression and

draw

Consider the following Boolean expression A(B + C)

• Now compare the final result column in this truth table to the truth table for the previous example• They are identical



Now let’s go the other way; let’s take a Boolean expression and draw

We have therefore just demonstrated circuit equivalence

That is, both circuits produce the exact same output for each input value combination

Boolean algebra allows us to apply provable mathematical principles to help us design logical circuits



Homework

Read Chapter Four, Sections 4.4 – 4.7Exercise: P119-120, 55 & 59



Chapter 5

Computer Components



Communication

Application

Operating System

Programming

Hardware

Information

Layers of a Computing System

Hofstra University – Overview of Computer Science, CSC005 8

Chapter Goals

Read an ad for a computer and understand the jargon

List the components and their function in a von Neumann machine

Describe the fetch-decode-execute cycle of the von Neumann machine


Chapter Goals

Describe how computer memory is organized and accessed

Name and describe different auxiliary storage devices

Define three alternative parallel computer configurations


Computer Components

Consider the following ad


Sizes in Perspective

Admiral Grace Murray Hopper A coil of wire nearly 1,000 feet long

Distance traveled by an electron along the wire in the space of a microsecond

A short piece of wireIn the space of a nanosecond

A bag containing grains of pepperIn the space of a picosecond


Sizes in Perspective


Stored-Program Concept

Figure 5.1 The von Neumann architecture

Von Neumann Bottleneck


John von Neumann

Hungrain born mathematician

Orignal member of Institute of Advanced Studies at Princeton where he met Alan Turing

Member of the Manhattan Project

Responsible for modern computer design – the “stored – program computer”

Fly and the Train Problem!

Hofstra University – Overview of Computer Science, CSC005

Memory

Memory is a collection of cells,each with a unique physical address


Arithmetic/Logic Unit

Performing basic arithmetic operations such as adding

Performing logical operations such as AND, OR, and NOT

Most modern ALUs have a small amount of special storage units called registers


John Vincent Atanasoff

Native of Hamilton, NY

Envisioned a computer device that was “digital”

The idea of building an electronic digital computer came to him while he was sitting in a tavern – first computer insomniac

1939, the Atanasoff Berry Computer (ABC) at University of Iowa

Forgotten “Father of the Computer”


Input/Output Units

Input Unit A device through which data and programs from the outside world are entered into the computer

Keyboard, the mouse, and scanning devices

Output unit A device through which results stored in the computer memory are made available to the outside world

Printers and video display terminals


Herman Hollerith

Developed calculating method for 1890 census

Based on Hollerith code using card with holes punched in them

1896 founded the Tabulating Machine Company

1911 merged with another company to form the Computing Tabulating Recording (CTR) company, with Thomas J Watson president

1924 company renamed IBM


Control UnitControl unit The organizing force in the computer

There are two registers in the control unitThe instruction register (IR) contains the instruction that is being executedThe program counter (PC) contains the address of the next instruction to be executed

ALU and the control unit called the Central Processing Unit, or CPU


Flow of Information

The parts are connected to one another by a collection of wires called a bus

Figure 5.2 Data flow through a von Neumann architecture


The Fetch-Execute Cycle

Fetch the next instruction

Decode the instruction

Get data if needed

Execute the instruction


Figure 5.3 The Fetch-Execute Cycle


RAM and ROM

RAM stands for Random Access MemoryInherent in the idea of being able to access each location is the ability to change the contents of each location

ROM stands for Read Only MemoryThe contents in locations in ROM cannot be changed

RAM is volatile, ROM is notThis means that RAM does not retain its bit configuration when the power is turned off, but ROM does


Secondary Storage Devices

Because most of main memory is volatile and limited, it is essential that there be other types of storage devices where programs and data can be stored when they are no longer being processed

Secondary storage devices can be installed within the computer box at the factory or added later as needed


Magnetic Tape

The first truly mass auxiliary storage device was the magnetic tape drive

Figure 5.4 A magnetic tape

5-17


Tape Silo

Handled by a robotTravels 80 mph


Magnetic Disks

A read/write head travels across a spinning magnetic disk, retrieving or recording data

Figure 5.5 The organization of a magnetic disk


A Hard Drive In Action

Inside A Hard Drive - Simple operations performed by a hard drive with no cover, so that you can see what it looks like inside. This experiment was performed on an old hard drive, do not try this with newer expensive hard drives, it is a bit risky. -from digg.com

What Happens When You Drop A DIsk - Or Two!


Compact Disks

A CD drive uses a laser to read information stored optically on a plastic disk

CD-ROM is Read-Only Memory

DVD stands for Digital Versatile Disk


USB Drive

Flash Drive is a form of non-volatile memory

Stores information in an array of floating gate transistors, called "cells"


Touch Screens

Touch screen A computer monitor that can respond to the user touching the screen with a stylus or finger

There are four typesResistiveCapacitive Infrared Surface acoustic wave (SAW)


Touch Screens

Resistive touch screen A screen made up of two layers of electrically conductive material.

One layer has vertical lines, the other has horizontal lines. When the top layer is pressed, it comes in contact with the second layer which allows electrical current to flow.The specific vertical and horizontal lines that make contact dictate the location on the screen that was touched.


Touch Screens

Capacitive touch screen A screen made up of a laminate applied over a glass screen.

The laminate conducts electricity in all directions, and a very small current is applied equally on the four corners. When the screen is touched, current flows to the finger or stylus. The location of the touch on the screen is determined by comparing how strong the flow of electricity is from each corner.


Touch Screens

Infrared touch screen A screen with crisscrossing horizontal and vertical beams of infrared light

Sensors on opposite sides of the screen detect the beams.

When the user breaks the beams by touching the screen, the location of the break can be determined.


Touch Screens

Surface acoustic wave (SAW) A screen with crisscrossing high frequency sound waves across the horizontal and vertical axes.

When a finger touches the surface, the corresponding sensors detect the interruption and determine the location of the touch.


Synchronous processing

One approach to parallelism is to have multiple processors apply the same program to multiple data sets

Figure 5.7 Processors in a synchronous computing environment


Pipelining

Arranges processors in tandem, where each processor contributes one part to an overall computation

Figure 5.8 Processors in a pipeline


Independent Processingwith Shared Memory

Figure 5.9 A shared-memory configuration of processors



Assignment One

Let Me Know If I Can Publish On Web SiteThere Is No Obligation



Homework

Read Chapter Five, All Sections



Mid-Term

Take Home Exam – Non-Trivial (think!)Cover Chapters 1-5 & 16 & Anything Covered In ClassGiven Out: Oct 11Due Back: Oct 18 No Lateness!!!



Good Night and Good Dreams!

9/19/06 hofstra university – overview of computer science, csc005 1 combinational circuits gates...

Documents